Process for 1,3,3,3-tetrafluoropropene

ABSTRACT

The present invention provides a simple three step process for the production of 1,3,3,3-tetrafluoropropene (HFO-1234ze). In the first step, carbon tetrachloride is added to vinyl fluoride to afford the compound CCl 3 CH 2 CHClF (HCFC-241fb). HCFC-241fb is then fluorinated with anhydrous HF to afford CF 3 CH 2 CHClF (HCFC-244fa) in the second step. Dehydrochlorination of HCFC-244fa, in the third step, affords the desired product, CF 3 CH═CHF (HFO-1234ze). Following similar chemistry, vinyl chloride may be used in place of vinyl fluoride.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims domestic priority under 35 U.S.C. 119(e) tocommonly owned U.S. Provisional Application Ser. No. 61/598,523, filed14 Feb. 2012, the disclosure of which is hereby incorporated herein byreference.

FIELD OF THE INVENTION

The present invention describes a process for making the compound1,3,3,3-tetrafluoropropene (CF₃CH═CHF, HFO-1234ze or 1234ze). Thedescribed process is industrially applicable for making 1234ze fromcommercially available raw materials.

BACKGROUND OF THE INVENTION

The tetrafluoropropene compound 1234ze is a useful compound with lowglobal warming potential which is used in many applications. Forexample, CF₃CH═CHF is useful as a foam blowing agent, refrigerant, andas monomer for homopolymers and copolymers.

Several methods for the preparation of CF₃CH═CHF are known. For example,U.S. Pat. No. 6,548,719 describes the production of many fluoro-olefinsincluding CF₃CH═CHF from CF₃CH₂CF₂H (245fa) by dehydrohalogenation inthe presence of a phase transfer catalyst. U.S. Pat. Nos. 5,986,151 and6,124,510 describe the gas phase catalytic dehydrofluorination ofCF₃CH₂CF₂H to afford CF₃CH═CHF. These documents are hereby incorporatedherein by reference.

Gas phase dehydrochlorination of CF₃CH₂CHFCl (244fa) is reported to giveCF₃CH═CHF as described in U.S. Pat. No. 7,829,748. Vapor phasefluorination of CF₃CH═CHCl (1233zd) with HF with SbF₅ catalyst affordsHFO-1234ze along with 245fa. See, for example, U.S. Pat. No. 7,829,748.This document is hereby incorporated herein by reference.

The main disadvantages of the above described methods are that in eachcase the starting materials, for example CF₃CH₂CF₂H, typically need tobe made in multiple reaction steps, and/or with relatively expensive rawmaterials, and thus there is a need to provide an improved (oralternate) process for the production of HFO-1234ze, at least from acost effectiveness viewpoint. Accordingly, the present invention hasbeen developed, namely a process which utilizes relatively inexpensiveand commercially available starting materials for making HFO-1234ze asdetailed below.

SUMMARY OF THE INVENTION

The present invention provides a simple three step process for theproduction of 1,3,3,3-tetrafluoropropene (HFO-1234ze). In the firststep, carbon tetrachloride is added to vinyl fluoride to afford thecompound CCl₃CH₂CHClF (HCFC-241fb). HCFC-241fb is then fluorinated withanhydrous HF to afford CF₃CH₂CHClF (HCFC-244fa) in the second step.Dehydrochlorination of HCFC-244fa, in the third step, affords thedesired product, CF₃CH═CHF (HFO-1234ze).

One embodiment of the present invention provides a simple three stepprocess as depicted below:

CH₂═CHF+CCl₄→CCl₃CH₂CHClF   (1)

(addition)

CCl₃CH₂CHClF→CF₃CH₂CHClF   (2)

(HF)

CF₃CH₂CHClF→CF₃CH═CHF   (3)

(−HCl)

In another embodiment, vinyl chloride can be used in place of vinylfluoride, such that the process has the following three steps:

CCl₄+CH₂═CHCl→CCl₃CH₂CHCl₂   (1)

CCl₃CH₂CHCl₂→CF₃CH₂CFHCl   (2)

CF₃CH₂CFHCl→CF₃H═CHF   (3)

DETAILED DESCRIPTION OF THE INVENTION

As shown in the above depicted reactions, the process comprises threesteps:

Step (1)—addition of carbon tetrachloride to vinyl fluoride/chloride,

Step (2)—fluorination of the resultant product with HF, and

Step (3)—dehydrochlorination of the compound from step (2).

Thus, in one embodiment of the first step, carbon tetrachloride is addedto vinyl fluoride to afford compound CCl₃CH₂CHClF (HCFC-241fb) which isthen fluorinated with HF, preferably anhydrous HF, to afford CF₃CH₂CHClF(HCFC-244fa) in the second step. Fluorination reactions are typicallycarried out with hydrogen fluoride, preferably anhydrous HF (AHF) and afluorination catalyst. These catalysts are well known, and one can finetune the reaction conditions to afford mainly the desired product.Dehydro-chlorination of CF₃CH₂CHClF (HCFC-244fa), in the third step,affords CF₃CH═CHF (HFO-1234ze).

In certain embodiments, the addition reaction of CCl₄ to CH₂═CHF wasconducted in the presence of triethylphosphate and iron powder atelevated temperature (120° C. to 130° C.) to afford CCl₃CH₂CHClF(HCFC-241fb), in good yield.

Iron nano particles and/or nano powder, which are commerciallyavailable, can also be employed for the addition reaction instead ofiron powder. Iron nano particles can be on a support such as activatedcarbon. The advantage of Fe nanopowder is its large surface area thusreducing its amount as well as time required for the reaction.

In certain embodiments, the HCFC-241fb was fluorinated with three (3)equivalents of anhydrous HF in the presence of a fluorination catalystsuch as SbCl₅ to afford CF₃CH₂CHClF (see for example U.S. Pat. No.7,829,748). By-products such as CF₃CH═CHCl (HCFO-1233zd) or CF₃CH═CHF(HFO-1234ze) which may be formed can easily be separated from the higherboiling HCFC-244fa, for example, by distillation. Also, the fluorinationreaction conditions may be fine-tuned in such a way that the desiredCF₃CH₂CHClF is predominantly obtained.

In certain embodiments, the fluorination reaction is carried out in aMonel® tube reactor which is charged with a premade fluorinationcatalyst such as SbCl₅ (or SbF₅ or SbCl_(x)F_(y), where x+y=5) onactivated carbon (Togo Calgon PCB, 4×10 mesh) and heated to about 70° C.to 85° C. (see U.S. Pat. No. 7,829,748). Then a mixture of vaporizedCCl₃CH₂CHClF and anhydrous HF (AHF) in a ratio of about 1:10 is passedthrough the heated catalyst bed in the reactor with a contact time offrom 2 sec to 10 sec. Contact time=bulk volume of catalyst/volumetricflow rate of reactants in ml/sec. The flow rate of each reactant wascontrolled with a mass flow meter/controller in such a way that thecontact time is maintained in the range of 2 sec. to 10 sec.

The effluent from the reactor was analyzed by GC/GC-MS foridentification the products. CF₃CH₂CHClF (HCFC-244fa) was obtained asthe main product; the by-products were CF₃CH₂CF₂H (HFC-245fa) andCF₃CH═CHCl (HCFC-1233zd) which could easily be separated from the higherboiling HCFC-244fa (bp=30° C. at 27 psi) by distillation.

Dehydrochlorination of CF₃CH₂CHClF can either be carried out in liquidor gas phase with an appropriate catalyst, as taught for example, inU.S. Patent Pub. No. 2007-0129580, U.S. Pat. No. 7,829,748 and PCTPublication No. WO 2009/0211542. Many catalysts can be used fordehydrochlorination depending on the reaction conditions. For liquidphase reactions, typical catalysts are sodium or potassium hydroxidewith a phase transfer catalyst, as taught in U.S. Pat. No. 7,829,748.These documents are hereby incorporated herein by reference.

In certain embodiments, the vapor phase dehydrochlorination is conductedat a temperature range of from about 300° C. to 500° C. This process canbe effected with a number of catalysts, including for example, acidtreated activated carbon, or a mixture metal chloride and metal fluoridecatalysts, for example CsCl+MgF₂ in a 1:9 ratio.

All processes described here can be run in a continuous manner eitherindividually or as a combination of some or all of the individualprocess steps. As will be appreciated by those having ordinary skill inthis art, various reaction modifications can be implemented for betterselectivity and yield in each of the reaction steps described herein.

EXAMPLES Example 1 Addition of CCl₄ to CH₂═CHF

To a clean, dry and leak tested 1 L autoclave was added iron powder (5.0g, 89 mmol), triethylphosphate (22.5 g, 89 mmol) and carbontetrachloride (425 g, 2.76 mol) under nitrogen purge. The autoclave waspurged with nitrogen for 3 minutes and evacuated. To the evacuatedautoclave was introduced vinyl fluoride (157 g, 2.70 mol), and thepressure was from about 58 psi to 60 psi. The stirred contents in theautoclave were then heated to and maintained at a temperature from 120°C. to 125° C. for 8 hours at a pressure about 120 psi.

An additional 10 g of triethylphosphate (39 mmol) was injected into theautoclave and heated for additional 10 hours at 120° C. to 125° C. Theautoclave was cooled to 25° C. and the contents were poured into coldwater (about 1 L), the organic layer separated, washed thrice withwater, dried over MgSO₄ and filtered. The crude material was distilledat 63° C. to 65° C. to afford 470 g (yield=81%) of CCl₃CH₂CHClF.

Example 1a

The reaction of Example 1 was again carried out except that Fe nanopowder (2.0 g, 36 mmol) and triethyl phosphate (9.1 g, 36 mmol) wereused and heated for 5 hrs at 120-130° C. at pressure of about 110 to 120psi. The work up and isolation was the same as described for the aboveexample; yield ranged from 60-85% .

Example 2 Fluorination of CCl₃CH₂CHClF to CF₃CH₂CFHCl

The fluorination reaction was conducted in a Monel® tube reactor (2.54cm diameter, 80 cm long). The reactor was then charged with 150 g offluorination catalyst, as described in U.S. Pat. No. 7,829,748, SbCl₅ onactivated carbon (Toyo Colon PCB, 4×10 mesh), and heated to 85° C. Thena mixture of vaporized CCl₃CH₂CHClF and anhydrous HF (1:10) was passedthrough the heated catalyst with a contact time of from 2 sec. to 10sec. Contact time=bulk volume of catalyst/volumetric flow rate ofreactants in ml/sec. The flow rate of each reactant was controlled witha mass flow meter-controller in such a way that the contact time was inthe range of from 2 sec. to 10 sec.

The effluent mainly consisted of CF₃CH₂CHClF (HCFC-244fa). For example,with a contact time of 2 sec., at 65° C. to 70° C., the yield ofCF₃CH₂CHClF ranged from 40% to 50% as determined by GC area; theremainder being by-products including CF₃CH₂CF₂H (HFC-245fa) andCF₃CH═CHCl (HCFC-1233zd) about 1:1, HCFC-244fa which were separated bydistilling.

Example 3 Dehydrochlorination of CF₃CH₂CHClF

A. Liquid Phase:

Into a 0.5 L Teflon lined autoclave was charged 300 g of 20% aq. KOHsolution, 1 g Aliquat 336 or 18-crown ether and 20 g CF₃CH₂CHClF. Thecontents in the autoclave were heated to and maintained at from 50° C.to 55° C. for 6 hours. The progress of the reaction was monitored by GC.After 12 hours, the product HFO-1234ze (65% yield) was collected in asteel cylinder cooled at −78° C.

B. Vapor phase:

In a Monel tube reactor, 20 cc of acid treated (HCl or HNO₃) catalystwas loaded and heated to 350° C. to 370° C. Then vapor stream ofCF₃CH₂CHClF at a rate about 6 g/h was passed through the heated catalystbed in the reactor for from 1 hour to 8 hours. The conversion ofHCFC-244fa ranged from 40% to 60% with a selectivity of HFO-1234zegreater than 95%. Further purification was accomplished by distillation.

Example 4 Addition of CCl₄ to CH₂═CHCl

This reaction was conducted in essentially the same manner as Example 1,except for the fact that instead of vinyl fluoride, an equivalent amountof vinyl chloride was used for the reaction. After work up anddistillation, 65% yield of CCl₃CH₂CHCl₂ was obtained.

Example 5 Reaction of CCl₃CH₂CHCl₂ with HF

This reaction was carried out in a 1 gallon Hastelloy C reactor byreacting CCl₃CH₂CHCl₂ with HF using TiCl₄ as the catalyst. Typically,1.4 lb of anhydrous HF and 0.15 lbs of TiCl₄ was added to the reactor;HCl was formed immediately which was vented and passed through ascrubber. After venting HCl gas 5 lbs of CCl₃CH₂CHCl₂ was added and thereactor was heated to 85° C. and the system pressure was maintained ataround 120 psig. Additional HF was then added and the product was streamwas collected in cold trap.

The products formed, as analyzed by GC, are CF₃CH═CHF, as well asCF₃CH₂CHClF, CF₃CH═CHCl, and CF₃CH₂CF₂H. The reaction conditions werefine-tuned such that the major products were CF₃CH═CFH, CF₃CH₂CHClF(combined 50%) besides the other by-products. The CF₃CH═CFH thus formedwas separated by distillation and the CF₃CH2CHClF is dehydrochlorinatedto CF₃CH═CFH as described in Example 3.

Alternately, 240fa can be passed through a Monel or nickel tube reactorwith HF (10 to 20 fold excess) over a catalyst such as metal powder forexample Al, Zn, Mg, Ni, Ti, Co on carbon support at elevated temperature(200° C. to 500° C.) with a contact time of 5 sec. to 20 sec. Thereaction conditions temperature, contact time, flow rate of CCl₃CH₂CHCl₂and HF are fine-tuned and selected with few runs such that the mainproduct formed is CF₃CH═CHF.

As used herein, the singular forms “a”, “an” and “the” include pluralunless the context clearly dictates otherwise. Moreover, when an amount,concentration, or other value or parameter is given as either a range,preferred range, or a list of upper preferable values and lowerpreferable values, this is to be understood as specifically disclosingall ranges formed from any pair of any upper range limit or preferredvalue and any lower range limit or preferred value, regardless ofwhether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range. It is not intended that the scope of the invention be limitedto the specific values recited when defining a range.

It should be understood that the foregoing description is onlyillustrative of the present invention. Various alternatives andmodifications can be devised by those skilled in the art withoutdeparting from the invention. Accordingly, the present invention isintended to embrace all such alternatives, modifications and variancesthat fall within the scope of the appended claims.

What is claimed is:
 1. A process for the production of1,3,3,3-tetrafluoropropene (HFO-1234ze) comprising the steps of: (a)reacting carbon tetrachloride with vinyl fluoride to afford the compoundCCl₃CH₂CHClF (HCFC-241fb); (b) fluorinating HCFC-241fb with HF to affordthe compound CF₃CH₂CHClF (HCFC-244fa); and (c) dehydrochlorinatingHCFC-244fa to produce the compound CF₃CH═CHF (HFO-1234ze).
 2. A processfor the production of 1,3,3,3-tetrafluoropropene (HFO-1234ze) comprisingthe steps of: (a) reacting carbon tetrachloride with vinyl chloride toafford the compound CCl₃CH₂CHCl₂; (b) fluorinating the compoundCCl₃CH₂CHCl₂ to generate the compound CF3CH2CHClF (HCFC-244fa); and (c)dehydrochlorinating HCFC-244fa to produce the compound CF₃CH═CHF(HFO-1234ze).
 3. The process of claim 1, wherein the reaction of carbontetrachloride with the vinyl halide compound is conducted in thepresence of triethylphosphate and an iron material selected from thegroup consisting of supported or unsupported iron powder, ironnanopowder and iron nanoparticles, at an elevated temperature.
 4. Theprocess of claim 3, wherein the elevated temperature is from about 120°C. to 130° C.
 5. The process of claim 1, wherein the step (b)fluorination reaction is conducted with an excess equivalent of hydrogenfluoride in the presence of a fluorination catalyst.
 6. The process ofclaim 5, wherein at least three equivalents of hydrogen fluoride areused.
 7. The process of claim 5, wherein the hydrogen fluoride isanhydrous.
 8. The process of claim 5, wherein fluorination catalyst hasthe formula SbCl_(x)F_(y), wherein x+y=5.
 9. The process of claim 8,wherein fluorination catalyst comprises SbCl₅.
 10. The process of claim8, wherein fluorination catalyst comprises SbF₅.
 11. The process ofclaim 5, wherein any by-products formed during the fluorination reactionare separated from the HCFC-244fa.
 12. The process of claim 11, whereinone by-product comprises the compound CF₃H═CHCl (HCFO-1233zd).
 13. Theprocess of claim 11, wherein one by-product comprises the compoundCF₃CH═CHF (HFO-1234ze).
 14. The process of claim 1, wherein thedehydrochlorination reaction of CF₃CH₂CHClF is conducted in either theliquid phase or the gas phase, with a dehydrochlorination catalyst. 15.The process of claim 14, wherein the dehydrochlorination reaction isconducted in the liquid phase.
 16. The process of claim 14, wherein thedehydrochlorination reaction is conducted in the gas phase.
 17. Theprocess of claim 15, wherein the catalyst is selected from the groupconsisting of sodium or potassium hydroxide with a phase transfercatalyst.
 18. The process of claim 16, wherein the catalyst is selectedfrom the group consisting of acid treated activated carbon, and amixture metal chloride and metal fluoride catalysts.
 19. The process ofclaim 18, wherein the catalyst comprises CsCl+MgF₂ in a 1:9 ratio. 20.The process of claim 16, wherein the dehydrochlorination reaction isconducted at a temperature range of from about 300° C. to 500° C. 21.The process of claim 1, wherein the reactions are conducted in acontinuous manner.
 22. The process of claim 2, wherein the reactions areconducted in a continuous manner.
 23. The process of claim 2, whereinthe dehydrochlorination reaction of CF₃CH₂CHClF is conducted in eitherthe liquid phase or the gas phase, with a dehydrochlorination catalyst.24. The process of claim 2, wherein the step (b) fluorination reactionis conducted with an excess equivalent of hydrogen fluoride in thepresence of a fluorination catalyst.
 25. The process of claim 2, whereinthe reaction of carbon tetrachloride with the vinyl halide compound isconducted in the presence of triethylphosphate and an iron materialselected from the group consisting of supported or unsupported ironpowder, iron nanopowder and iron nanoparticles, at an elevatedtemperature.